S: (n) superfecundation (fertilization of two or more ova released during the same menstrual cycle by sperm from separate acts of coitus (especially by different males))
S: (n) superfetation (fertilization of a second ovum after a pregnancy has begun; results in two fetuses of different ages in the uterus at the same time) "superfetation is normal in some animal species"
S: (n) cross-fertilization, cross-fertilisation (interchange between different cultures or different ways of thinking that is mutually productive and beneficial) "the cross-fertilization of science and the creative arts"